VIEW ARTICLE

Biological Control

Suppression of the Nematode Heterodera schachtii by the Fungus Hirsutella rhossiliensis as Affected by Fungus Population Density and Nematode Movement. E. C. Tedford, Department of Nematology, University of California, Davis 95616-8668; B. A. Jaffee, and A. E. Muldoon. Department of Nematology, University of California, Davis 95616-8668. Phytopathology 85:613-617. Accepted for publication 27 February 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/Phyto-85-613.

We quantified penetration of roots by Heterodera schachtii as affected by two factors: the population density of Hirsutella rhossiliensis, and the distance that nematodes moved through soil. The fungus was added to soil in the form of pelletized hyphae, and the nematode was added to soil as second-stage juveniles (J2). Polyvinyl chloride tubes were filled with 27 cm³ of loamy sand containing 0.0, 0.25, 0.5, 1.0, or 2.0 pellets per cm³ of soil. In vitro, hyphae grew from each pellet and produced approximately 104,000 spores after 14 days at 20ºC. A cabbage seedling was planted in a hole 2 cm from one end of each tube, and J2 were added to holes either 2, 4, 6, or 8 cm from the seedling. Tubes were positioned vertically to prevent roots from growing toward nematodes and to confine roots to the bottom 2 cm of the tube. Penetration of roots by J2 was inversely related to pellet density and distance. Fifty percent suppression of root penetration required approximately 0.9, 0.3, and 0.2 pellets per cm³ of soil at distances of 2, 4, and 8 cm, respectively.